1. Technical Field
The present invention relates to a plating removing apparatus for a two-piece wheel which removes plating of a welding planned portion on an inner circumferential surface of a rim in a the two-piece wheel which has the rim and a disk.
2. Background Art
Widely practiced vehicle wheels made of aluminum alloys and other light alloys, include a one-piece wheel integrally formed by molding, a two-piece wheel configured by dividing the wheel into two parts that are a rim and a disk, and a three-piece wheel configured by dividing the wheel into three parts that are an inner rim, an outer rim, and a disk. Wheels subjected to a treatment of chromium plating or other plating to enhance their design features are also extensively put into practical use (refer to Japanese Unexamined Patent Publication No. Hei 11-236681).
In general, it is common to configure a two-piece wheel by plating only a disk and a rim is not plated because of the following reasons.
That is, in the two-piece wheel, in a state that the disk is fitted and fixed to an inside of the rim by shrink-fitting, an inner circumferential surface of the rim and an outer circumferential surface of the disk are welded to integrate the two into one. In the event that the rim and the disk are subjected to a plating treatment, the two must be welded by removing plating layers of welding planned portions thereof in order to prevent welding defects of the disk with respect to the rim. Because the plating layer of the welding planned portion on the disk is outwardly exposed, it is comparatively easy to remove the plating layer manually by the use of portable grinder or the like. However, because the plating layer of the welding planned portion on the rim is formed on an inner circumferential surface of the rim, while the disk must be fixed to a proper position in the axial direction of the rim, there is a problem in that the plating layer cannot be accurately removed by hand using a portable grinder, or the like.
In addition, in place of a plating removing treatment by a portable grinder or the like, it is possible to provide a configuration in which formation of a plating layer at a welding planned portion is prevented by affixing a masking tape to the welding planned portions when a rim is subjected to a plating process. However, in such event, in order to affix the masking tape to a proper position, marks such as marking-off line must be formed on an inner circumferential surface of the rim, and the masking tape must be affixed along the marks, causing an extremely troublesome process. In addition, since the plating treatment requires a special technique which is not carried out by a wheel manufacturer but by a manufacturer specialized in the plating process, there is a problem of a labor charge increased for affixing the masking tape in the plating process, resulting in an increase of the wheel manufacturing cost. Furthermore, since an inner circumferential surface of the rim is formed with delicate irregularities, even if the masking tape is neatly affixed, parts of a welding planned portion may be plated by an invasion of plating liquid between the masking tape and the rim when the rim is immersed in the plating liquid. As shown in FIG. 10, there is yet another problem expected in a boundary part 103 adjacent to a base material part 101 in a welding planned portion of a rim 100, in which an elevated part 104 is formed along a side edge of the masking tape in a plated area 102, forming a level difference at the boundary 103 between the base material part 101 and the plated area 102. Accordingly, plating is easily exfoliated by a physical shock, and an incomplete plated area 105 including, for example, a copper plating layer in the case of chromium plating, is formed as a substrate layer by the plating liquid invaded between the masking tape and the rim, causing the plated area 102 to be easily exfoliated from the incomplete plated area 105.
Furthermore, there is considered a method to remove plating of a welding planned portion by cutting or the like in a machine process after performing a plating treatment, in place of a plating removal treatment by a portable grinder or the like. However, in such event, cutting the plated area by a single cutting treatment causes a force exerted on the plated area in the direction to exfoliate the plating when the cutting tool is withdrawn from the plated area, resulting in a problem of easy exfoliation of the plated area from the boundary adjacent to the base material portion. In addition, in order to prevent this, it is considered to insert the cutting tool from both side edges of the welding planned portion and to withdraw the cutting tool at halfway in the width direction of the welding planned portion. However, it is required to perform the cutting treatment twice, resulting in a troublesome process which is problematic.